1. Field of the Invention
This invention relates to means for the enhancement of the appearance of signs, particularly writable display signs.
2. Description of the Related Art
Writable display signs typically have an array of display elements which are controllable (usually electromagnetically) to display in an ON position, a bright surface for viewing by a viewer in a viewing direction and in an OFF position, a dark surface for viewing by a viewer in the viewing direction. The array may be activated so that the elements provide information or a different form of display.
Usually the elements are arranged as pixels in an array and usually, in such array, the pixels are arranged in rows and columns.
The bright surface displayed in the ON position is more or less clearly visible dependent upon the ambient light. In many applications, therefore, it is desirable to illuminate the array so the bright surfaces appear more brightly and contrast more with the dark surfaces.
Prior ways have been found to illuminate such elements but these have tended to increase the depth required by the array or increased the expense of making or operating such sign. In such an application as a vehicle destination sign, the increase in depth tends to increase the distance of the array from the windshield reducing the angle over which the array may be read.
There is herein provided a method of and means for illuminating the array of a changeable display sign comprising providing a transparent sheet in front of said array, so that the viewing direction for the sign passes through the transparent sheet.
The transparent sheet is typically the transparent front wall of a casing for the array. It could also be the windshield of a bus or other vehicle.
Using a vehicle windshield or vehicle window as the front transparent sheet would have some advantages since it would provide a wide angle for viewers located outside the vehicle. However using the vehicle windshield or window is usually inconvenient since its manufacture is primarily associated with the vehicle, rather than with the sign.
In accordance with the invention, the illumination for the array will be lights mounted on the transparent sheet and directed towards the array, that is away from the viewer. Thus the lights illuminate the bright surfaces of those elements which are in ON position for display in the viewing direction. This is a simple and easy way of increasing the contrast and hence the clarity of the sign without unduly increasing its depth.
Although the terminology used herein generally speaks of a sign viewable from the front, signs may equally be installed to be viewable from the back or sides or may be located elsewhere than on a vehicle.
In a preferred form of the above invention, the lights are light emitting diodes or LEDs.
The display elements may be of many different forms. They will quite commonly be rotatably mounted disks which are bright on one side and dark on the other, so that the bright and dark side of an element are displayed to the viewing direction in the ON and OFF positions, respectively, of the disks.
The transparent sheet may, if desired, be made flexible to conform to a curved space, such as inside a curved bus windshield.
When the illumination is by LEDs, these are preferably connected across gaps in a circuit applied to the transparent sheet to shine in a direction away from the viewer and toward the display elements. The conductor is usually a conducting ink which is usually opaque but relatively insignificant and not noticeable to the viewer.